1. Field of the Invention
The present invention relates to a method for producing phenol resin foams and also relates to a method of making composite foamed laminates comprising phenol resin foams and rigid polyurethane foams. They can be utilized suitably as heat insulating material for building structures and warm and cold water pipeways, bath tanks, etc. as well as floor base material with an aim of heat insulation or keeping air tightness in railway vehicles, etc.
2. Description of the Prior Art
As has been well-known, resol phenol resin foams are produced by admixing blowing agent, foam stabilizer and an acidic catalyst to liquid resol phenol resin under stirring thereby causing them to foam along with the progress of the resinification.
However, since the resol phenol resin foams have usually been produced by utilizing polycondensating reaction, there has been a problem that foaming cure requires a long time. Further, since the conventional resol phenol resin foams are hard and friable, the resultant foams involve drawbacks that the adhesion to various plate materials such as plywood, craft paper, plaster board, etc. or to concrete bodies is inferior.
Accordingly, it has been very difficult and lacked in practicaly to utilize the resol phenol resin foams as a substitute for rigid polyurethane foams in sprayed-in-place foaming applied so far by using rigid polyurethane foams.
On the other hand, the rigid polyurethane foams have low thermal conductivity and excellent thermal insulating property, and have been utilized generally for laminated board, etc. They are useful for sprayed-in-place foaming process.
However, the rigid polyurethane foams are easily ignited by merely brought into contact with small firing source such as welding sparks to possibly lead to fire accidents, thereby bringing about a problem in view of the fire proofness.
Although phenol resin foams which also have been suitably used as laminated boards, etc. are excellent in fire proofness, they involve a problem that the heat insulating performance is rather poor as compared with the rigid urethane foams.
In view of the above, it has been desired for foam structure having both high fire-proofness and excellent heat insulating property.